Methods for producing 1,3-butadiene, the demand and value of which are gradually increasing as an intermediate of petrochemical products in the petrochemical industry, include naphtha cracking, direct dehydrogenation of normal-butene, and oxidative dehydrogenation of normal-butene.
Of these, oxidative dehydrogenation (ODH) of normal-butene to produce butadiene has advantages of reducing energy consumption because it is an exothermic reaction that may be performed at a low temperature, unlike direct dehydrogenation, and of inhibiting carbon deposition and removing the carbon deposits by addition of an oxidant during dehydrogenation. Various metal oxides are used as catalysts for oxidation/dehydrogenation of butane. In particular, a bismuth molybdenum-based catalyst which is a composite of bismuth oxide and molybdenum oxide is known to exhibit superior activity.
The bismuth molybdenum-based catalyst includes pure bismuth molybdate catalysts composed of only bismuth and molybdenum oxides and multi-component bismuth molybdate catalysts containing various other metals. Production of 1,3-butadiene through oxidative dehydrogenation of normal-butene in the presence of a pure bismuth molybdate catalyst is unsuitable for commercial processes due to limitation in increasing a yield of 1,3-butadiene. As an alternative to the pure bismuth molybdate catalyst, production of multi-component bismuth molybdate catalysts containing various other metals, in addition to bismuth and molybdate, is actively researched to improve activity of bismuth molybdate catalysts in oxidative dehydrogenation of normal-butene.
When only 1-butene having relatively high reactivity among normal-butenes is used as a reactant to obtain 1,3-butadiene at a high yield, or a C4 mixture containing normal-butane and normal-butene is used as a reactant in the production of 1,3-butadiene using a multi-component bismuth molybdate catalyst, very complicated multi-component bismuth molybdate catalysts including a combination of more types of metals are used. That is, metals are continuously added to improve catalytic activity, thus disadvantageously making catalyst components considerably complicated, making synthesis route for producing catalysts complicated and making it difficult to obtain reproduction. In addition, in the prior art, only pure normal-butene (1-butene or 2-butene) is used as a reactant, or a C4 mixture having a low normal-butane content less than 10% by weight is used as a reactant although a mixture of normal-butane and normal-butene is used as the reactant. Accordingly, when a C4 mixture having a high normal-butane content is used as the reactant, yield of 1,3-butadiene becomes lower.
In addition, C4 mixtures that may be easily obtained by an actual petrochemical process have a high content of normal-butane and require further separation of normal-butene so as to apply catalysts used in the prior art to commercial processes and thus inevitably cause great deterioration in economic efficiency.